Promise of increased spectral efficiency with LTE-U small cell deployments is balanced with potential for Wi-Fi interference
WASHINGTON – Earlier this week federal regulators solicited input from telecom stakeholders regarding feedback on LTE-Unlicensed, particularly as the emerging technology relates to Wi-Fi networks.
LTE-U, which was developed by chipmaker Qualcomm, uses the same 5 GHz unlicensed spectrum band that’s occupied by Wi-Fi networks.
The response to the Federal Communications Commission’s request for input has so far drawn comment from 36 companies including Nokia, Huawei, Microsoft, Google, T-Mobile US and other stakeholders.
Qualcomm sees LTE-U as ideal for both outdoor and indoor small cell deployment. Using licensed assisted access, LTE-U is said to be able to significantly increase network capacity.
It’s Qualcomm’s position that LTE-U can provide the same security and flexibility as Wi-Fi while not interfering with Wi-Fi, a primary concern mentioned in the FCC’s public notice.
A Nokia test of LTE-U interaction with Wi-Fi noted, “LTE system performance is slightly affected by coexistence whereas Wi-Fi is significantly impacted by LTE transmissions. In coexistence, the Wi-Fi channel is most often blocked by LTE interference, making the Wi-Fi nodes stay on the listen mode more than 85% of the time. This reflects directly on the Wi-Fi user throughput, that decreases from 50% to [approximately] 100% depending on the scenario.”
The Nokia test went on to conclude that by putting “reasonable coexistence mechanisms” in place, “it was shown that LTE-U behaves as a comparable or better neighbor to Wi-Fi.”
Response to the FCC request for comment has been severely split.
Leading U.S. carrier Verizon Communications noted in its filing, “The communications industry must innovate and invest to meet consumers’ exploding demand for wireless bandwidth. Part of that investment must be in new technologies that minimize the amount of spectrum needed to provide high-speed wireless data services. Verizon and its technology partners are developing and deploying a next-generation technology, LTE-Unlicensed, which will efficiently use unlicensed spectrum for data-intensive needs, such as downloading mobile apps and streaming video.”
Verizon reps went on to say that the company plans to deploy LTE-U small cells in areas where spectral capacity is strained
“Customers served by LTE-U will enjoy all the advantages of ‘standard’ LTE, including fast download speeds and seamless coverage when moving between cells. And because LTE-U is a highly spectrum-efficient way to provide data service, its use will minimize overall congestion in the unlicensed ecosystem. Efficient overall use of unlicensed spectrum benefits all consumers, including ones using other unlicensed technologies such as Wi-Fi, by minimizing all providers’ spectrum constraints.”
Google was less enthusiastic in its filing: “Two aspects of LTE-U, in particular, affect Wi-Fi transmissions. First, LTE-U’s approach to duty-cycling causes LTE transmissions to begin abruptly, often in the middle of Wi-Fi transmissions, interrupting them and causing Wi-Fi in the presence of moderate interference from LTE (below Wi-Fi’s prescribed energy detect level) experiences substantial degradation. In order to preserve unlicensed spectrum as a platform for permission less innovation, LTE operators must work with other users of unlicensed bands to overcome these technical issues and ensure that license-anchored systems will not systematically crowd out popular technologies that rely solely on unlicensed spectrum. To slow down throughput in response to increased error rates. Second, Wi-Fi operation in the presence of moderate interference from LTE (below Wi-Fi’s prescribed energy detect level) experiences substantial degradation. In order to preserve unlicensed spectrum as a platform for permission less innovation, LTE operators must work with other users of unlicensed bands to overcome these technical issues and ensure that license-anchored systems will not systematically crowd out popular technologies that rely solely on unlicensed spectrum.”
AT&T, meanwhile, tried to strike a more neutral tone, calling LTE-U a potentially “cost-effective and spectrally efficient way to help address the sky-rocketing demand for mobile broadband, though it cannot take the place of additional unlicensed spectrum. Through carrier aggregation, LTE unlicensed may allow carriers to gain additional network capacity by combining LTE in unlicensed bands with LTE in licensed bands. In turn, wireless operators will be able to offer consumers seamless user experiences across unified networks. With these important public interest benefits, the Commission should reject calls to prejudice this nascent technology by excluding it from unlicensed bands.”
